Pulsar Modules Only Working With Heat Applied

[bucko170]

I have a couple of Pulsar modules that work for short periods of time when heat is applied to them, I was wondering if this is due to a specific fault on the module or whether the same symptoms could be caused by a variety of faults?

I am unsure whether to send them off to Hanno for the SASM conversion or to send them off for repair, I don't mind the having the SASM converted modules so the deciding factor for me would be the cost.

I have also noted the same fault is common with NSC modules, is this just a coincidence or is there a common factor that is shared between the two modules?

[holly35]

Like my hamilton,it may have an oscillator fault.I was advised some 50% of modules with similar problems will die again after repair.As far as i can see, these modules from Hanno are fine.If you intend wearing it it should provide reliable performance . Worth remembering they are hand assembled (just like the early pulsar modules)and do use some original components.
Do you really want to power up and wear that flawless pulsar?
Can you trust yourself not to scrape that mint crystal?

[bucko170]

I wonder what the success rate is with a CMOS oscillator fitted as per this thread? http://www.dwf.nu/viewtopic.php?t=3918&highlight=

At £2.07 plus P&P it's cheap enough.

[digibloke]

Hi. When you warm up the module you're expanding the metal in there. If there's been a screwdriver scraped across a copper trace or if you have a cracked board then heating up a module may get it to work for a while by bridging a gap in a circuit (I've had this with NSC and bulova/Mostek modules). Pulsars have a maze of copper traces under the chip and it has been suggested that this is where the problem generally is when a QC is good and the watch shows a 0 or only works when heated.

I'e fitted a couple of CMOS oscillator chips on watches with this problem and they work fine. Worth a go at least before splashing out on a SASM and they're so small that you can leave the original crystal in place should you want to.

Your Navitimer look the business by the way

[bucko170]

I'e fitted a couple of CMOS oscillator chips on watches with this problem and they work fine. Worth a go at least before splashing out on a SASM and they're so small that you can leave the original crystal in place should you want to.

I purchase the Pulsar lot from 'Handy' and two of the modules have the oscillators fitted, both are working fine and keeping good time, and aesthetically they look OK so I think it is well worth giving them a try, I am useless with the soldering iron but one of the modules is with another forum member who hopefully will give it a go for me.

Your Navitimer look the business by the way

Cheers

[Old Tom]

The usual source of trouble with a module for a few hours that runs after heating is circuit board contamination from a battery that has leaked. Even when the board looks clean there may still be sufficient remnant electrolyte to stop the oscillator stage working. With the early modules the CMOS used is electronically "fragile" in the oscillator stage and even quite tiny shifts in feedback resistance or tuning capacitance will stop the oscillator running. Heating the module drives off the water being captured by the Potassium/Sodium Hydroxide that has leaked from the battery temporarily, but after a few hours the PH/SH sucks enough out of the enclosed atmosphere/batteries to become conductive again. To give some idea of the values involved typically an early CMOS oscillator will have a feedback resistor in the 1-20 Meg Ohm range, PH/SH contamination will effectively reduce this to 100K to 5 Meg Ohm, anything under about 700K will stop a simple CMOS inverter oscillator dead. Simple cure is to wash the circuit board thoroughly using organic acid solution, dilute bicarbonate solution, "dirty" water, "clean" water and isopropyl alcohol to remove the contamination. Pulsar modules make this difficult due to the black paint which acts like a sponge and is very reluctant to give up the PH/SH- removing the paint somrtimes works (but don't forget to send the board through the wash cycle afterwards).

Fitting a new crystal (and then finding the old crystal tests out fine!) often works because the solder flux locally removes the contamination that was stopping the oscillator- I hardly ever had have to replace "duff" crystals (perhaps three in twenty years!)- fault has been elsewhere.

Fitting one of the 32K oscillator chips (the SG-3030JF is probably the best, lowest current consumption and really tough when being soldered, some of us are not as good as we used to be back in the early 70s!) is an excellent cure for a damaged oscillator stage- I made myself a module tester based around one of these and promptly fixed two Ladies Pulsar modules (the SG3030 just fits!) and seven assorted Nat Semi modules (out of ten duff ones I had that had previously not responded to cleaning/crystal changes).

[bucko170]

Simple cure is to wash the circuit board thoroughly using organic acid solution, dilute bicarbonate solution, "dirty" water, "clean" water and isopropyl alcohol to remove the contamination.

Thank you Old Tom.

I have given it a go and they certainly look cleaner, I will allow them to dry for a few days before testing.

[retroleds]

Bicarbonate is actually alkaline, but that is good, alkaline will neutralize and break down acid salts, acids neutralize and break down alkaline. I use CLR diluted, but I consider the "flush" a last resort measure anyway, to be tried after blowing out with air(not too forceful) and/or distilled water and through drying have been tried. I figure the wire bonds below the IC are so thin, if acids have corroded them from all directions equally, then it is real wishful thinking that the removal of the acid salts made up(partially) of the corroded wirebonds is going to leave an intact wirebond.

[bucko170]

I ended up trying the wash on three modules two Pulsars and one NSC. I gave the modules 4 dips -

1. Vinegar.
2. Bicarbonate of soda (I thought this would neutralize the acid, it did give a lovely fizz .)
3. Distilled water.
4. Isopropanol.

Results.
It made no difference with the Pulsar modules, maybe due to the black paint covering the board? so these have been sent off to try with oscillators.
The NSC has definitely improved, it needed heating up to fire it up initially but it has been working on its own for a couple of days so I will have to wait and see what happens long term.

[graemec]

Hi,

Ive been looking at this thread with interest.
I bought a commodore MK1 watch as a non runner £20,
After reading this I put it on the radiator and wow it sprung into life.
This was not for long as when it got cold it stopped.
My guess is the oscillator stoppes as it will display only a few segments and freeze only by removing the batteries can I make it dormant and the radiator does the trick again.
It works on the wrist all day but wearing it in bed and in the morning it's dead again?

Any ideas??

I have an other NOS watch but it has a bubble LED display and it just isn't as good as the original one.